// Problem: 
// Contest: 
// URL: 
// Memory Limit: 
// Time Limit: 
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#include<bits/stdc++.h>
using namespace std;
#define int long long
inline int read(){
	int s=0,w=1;
	char ch=getchar();
	while(ch<'0'||ch>'9'){if(ch=='-')w=-1;ch=getchar();}
	while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
	return s*w;
}
struct mvs
{
	int m,v;
	double s;
};
bool cmp(mvs a,mvs b)
{
	if(a.s>b.s)return 1;
	return 0;
}
signed main()
{
	int n,t;
	cin>>n>>t;
	mvs arr[n];
	for(int i=0;i<n;i++)
	{
		cin>>arr[i].m>>arr[i].v;
		arr[i].s=(double)arr[i].v/arr[i].m;
	}
	sort(arr,arr+n,cmp);
	int i=0;
	double ans=0;
	while(t)
	{
		if(t>arr[i].m)
		{
			t-=arr[i].m;
			ans+=arr[i].v;
			i++;
		}
		else
		{
			ans+=t*arr[i].s;
			t=0;
		}
	}
	printf("%0.2lf",ans);
	return 0;
}
